Abstract

The Eyjafjallajökull ash that crossed over Spain and Portugal on 6e12 May 2010 has been monitored by
a set of operational sun photometer sites within AERONET-RIMA and satellite sensors. The sun
photometer observations (aerosol optical depth, coarse mode concentrations) and ash products from IASI
and SEVIRI satellite sensors, together with FLEXPART simulations of particle transport, allow identifying
the volcanic aerosols. The aerosol columnar properties derived from inversions were investigated,
indicating specific properties, especially regarding the absorption. The single scattering albedo was high
(0.95 at 440 nm) and nearly wavelength independent, although with slight decrease with wavelength.
Other parameters, like the fine mode fraction of the volume size distributions (0.20e0.80) or the portion
of spherical particles (15e90%), were very variable among the sites and indicated that the various ash
clouds were inhomogeneous with respect to particle size and shape.